The answer depends on what you want to factorise: 30, 303 (Oct 30 is the 303th day of the year), 41942 (days since 31 December 1899 = Excel day count).
30th, because it is divisible by 2, 3 and 5 which are all prime numbers.
17 October 1878
October 26th, 2001 fell on a Friday. The following year, October 26th fell on a Saturday.
October 9th, 1951 fell on a Tuesday. The following year, it fell on a Thursday.
October 10th, 1934 fell on a Wednesday. The following year it fell on a Thursday.
October 9th, 1985 fell on a Wednesday. The following year, it fell on a Thursday.
October 25th, 2002 fell on a Friday. The following year, it fell on a Saturday.
October 15th, 1855 fell on a Thursday. The following year it fell on Saturday.
October 9th, 2003 fell on a Thursday. The following year, it fell on a Saturday.
October 24th, 1948 fell on a Sunday. The following year, it fell on a Monday.
October 22nd, 1999 fell on a Friday. The following year, October 22nd fell on a Sunday.
Yes, October 31 is traditionally All Hallows Eve or Halloween, the following day being All Saints Day.